Examples of wedge-shaped flow meters are described in U.S. Pat. No. 4,237,739, which issued Dec. 9, 1980, and U.S. Pat. No. 4,926,698, which issued May 22, 1990. The '739 patent describes a flow meter which utilizes one wedge whereas the '698 patent describes a flow meter utilizing two wedges mounted on opposing sides of the tubular body or housing of the flow meter. These wedges in both patents require the flow to travel down the face of each wedge allowing the stream to flair out and contact the tube or cylinder wall, in which the wedge is mounted.
Examples of torus-shaped flow meters are described in U.S. Pat. No. 7,357,040, which issued Apr. 15, 2008 to Bell.
Accurate positioning and alignment of the fluid flow restriction member has continued to be a challenge. Accurate positioning of the flow restriction member, relative to the upstream and downstream sensors, is important in order to achieve reliable fluid flow measurements. Alignment of the flow restriction member, generally perpendicular to the direction of fluid flow, is important to prevent over pressuring of the member and to prevent distortion or bending of the member. Even though the wear component is usually only the flow restriction member, replacement in the field of only the flow restriction member has been impractical. Conditions in the field, such as those experienced along a pipeline, present difficult challenges in replacement of a flow restriction member. Performing the replacement procedure would require intricate position and alignment of the flow restriction member and intricate confirmation measurements. Several pieces would have to be positioned, aligned, and calibrated. The alignment and positioning with respect to the sensors and the direction of fluid flow have rendered field replacement impractical and unreliable unless the sensors and the flow restriction member are replaced as a single unit. There has been a long felt need to be able to replace the flow restriction member with greater ease and greater reliability while maintaining or even improving the measurement accuracy and repeatability. Further, there is a need to confirm that indeed a properly sized flow restriction member has been installed and also a need to track the history of the flow restriction member for maintenance prediction and/or application of correction factors to the measurements.